Mantas Enceris Athar Aziz The Settlement of Kansai International Airport Mantas Enceris Athar Aziz

INTRODUCTION Kansai International Airport is located on an artificial island in the middle of Osaka Bay, Japan The island is 4km long and 1km wide Construction started in 1987 The sea wall was finished in 1989 In 1990 3km bridge was completed to connect the island to the main land The airport opened in 1994

FORMATION OF THE SEA BED The undersea floor bed of Kansai International Airport is made up of sand and clay. The thickness of the layers increases as the sea deepens At the top of the formation the Holocene clay layer is approximately 20m in thickness The Holocene layer accumulated in the fourth Alluvial epoch 10,000 years ago to the present day always laying under the sea The Pleistocene layer consists of alternating layers of hard clay and gravel goes deep to hundreds of meters The Pleistocene layer can be divided into upper and lower parts The Pleistocene layer accumulated in the fourth Pleistocene epoch from approximately 2 million years ago to 10,000 years ago

THE SOIL OF THE SEA BED Clay layers accumulate on the seabed when the soil is under the sea Sand layers accumulate on the soil when the water level decreases and the soil emerges from the water

WHY SETTLEMENT OCCURS Approximately 70 percent of the soft alluvial clay contains water Even the hard Pleistocene clay contains 40 percent of water The weight of the artificial island presses the water out of the clay layers of the seabed, and causes the land to settle

CHARACTERISTICS OF THE SETTLEMENT OF THE HOLOCENE LAYER The settlement of the Holocene clay layer beneath the airport was stopped by artificially speeding up the process in less than a year The Sand Drain method was the solution to let the water out of the clay layer as fast as possible A million of sand drains (20m long and 40cm in diameter) were driven at 2.5m intervals into the clay layer under the island

CHARACTERISTICS OF THE SETTLEMENT OF THE HOLOCENE LAYER The settlement data of the Holocene clay layer shows that the settlement ended in less that a year after the reclamation land was loaded on and the Sand Drain method was employed The airport reclamation land has sunk very little since the alluvial settlement ended. Now settlement has completely ended

CHARACTERISTICS OF THE SETTLEMENT OF THE PLEISTOCENE LAYER The long-lasting, and ongoing settlement under the airport since its opening is still taking place in the Pleistocene layer The Pleistocene layer is sinks slowly and naturally over the long term

SETTLEMENT OF THE GROUND SURFACE The settlement of the man-made island can be almost attributed to the settlement of the settlement of the Pleistocene layer The settlement across the island varies depend on the thickness of the clay layer and the weight of the reclamation material The degree of the settlement decrease year by year and tending steadily towards an end

METHODS EMPLOYED AGAINST UNEQUAL SETTLEMENT Balance established by soil removal Compaction of the reclaimed layers Raft foundation Jack-up system

JACK-UP SYSTEM Main building is lighter then the adjacent structures The difference in the depth of the settlement generate slight tilts between the main building and the adjacent structures The pillars are jacked up under the main building in order to level the floor of the terminal